Alert archive / Nebraska / Mesoscale Discussions in 2021

Mesoscale Discussion 717

May 23, 20214 states

The Storm Prediction Center issued this mesoscale discussion at May 23, 2021, 6:53 PM MDT for 4 states. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued: May 23, 2021, 6:53 PM MDT (00:53 UTC)
Expired: May 23, 2021, 8:00 PM MDT
In force: 67 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 196

Counties Kit Carson County, CO, Phillips County, CO, Sedgwick County, CO, Yuma County, CO, Cheyenne County, KS, Sherman County, KS, Arthur County, NE, Chase County, NE, Deuel County, NE, Dundy County, NE, Garden County, NE, Grant County, NE, Keith County, NE, McPherson County, NE, Perkins County, NE, Sheridan County, NE, Bennett County, SD

The radar

The North Platte radar (KLNX), 140 km from the middle of the area, began a volume at 00:53 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 199May 23, 7:10 PM MDT

The nearest sounding before it

N. Platte/Lee Bi, NE (KLBF), launched 00:00Z, 0.9 hours before the alert went out and 116 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 930 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 1216 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 161 m²/s²
0-3 km storm-relative helicity: 229 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 7.0

Open this sounding in Storm Lab

The text

As transmitted.

597 
ACUS11 KWNS 240053
SWOMCD
SPC MCD 240053 
NEZ000-KSZ000-SDZ000-COZ000-240200-

Mesoscale Discussion 0717
NWS Storm Prediction Center Norman OK
0753 PM CDT Sun May 23 2021

Areas affected...Portions of Western/Central Nebraska...northwestern
Kansas

Concerning...Tornado Watch 196...

Valid 240053Z - 240200Z

The severe weather threat for Tornado Watch 196 continues.

SUMMARY...Storms have organized into line, particularly across
western Nebraska. As activity moves east, it is expected to be
maintained for another few hours. A new downstream severe
thunderstorm watch is likely soon as the expected transition to a
damaging wind threat.

DISCUSSION...Storm mode has become linear across most of Tornado
Watch 196 in Nebraska. Mid-level ascent and a developing low-level
jet is anticipated to sustain this activity for the next 2-4 hours
or so. This idea is also supported by the 00Z LBF sounding which
showed around 45 kts of effective shear and 1100 J/kg MLCAPE. With
this activity expected to move out of WW 196, parts of areas
downstream are likely to be included in a new watch soon. Though
low-level shear will be sufficient for embedded circulations within
the squall line, the primary threat is expected to be damaging wind
gusts with isolated large hail. The primary question will be how far
east the watch will extend downstream given relatively slow eastward
motion and low-level stabilization expected to occur.

..Wendt.. 05/24/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LBF...UNR...GLD...BOU...CYS...

LAT...LON   42210246 42730235 43110234 43290191 43190131 42460117
            41210108 39930140 39370136 39150170 39150255 39440280
            40190281 42210246

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 23, 6:32 PM MDT	Mesoscale Discussion	SPC	Baca, Prowers	118 min
May 24, 12:29 PM MDT	Tornado Watch	SPC	Cheyenne, Kit Carson, Prowers	9 hr
May 23, 7:12 PM MDT	Severe Thunderstorm Watch	SPC	Cheyenne, Decatur, Gove, Graham, Greeley, Logan and 7 more	5 hr
May 23, 8:56 PM MDT	Mesoscale Discussion	SPC	Cheyenne, Decatur, Logan, Rawlins, Sheridan, Sherman and 2 more	2 hr
May 24, 12:00 PM MDT	Mesoscale Discussion	SPC	Finney, Gove, Grant, Gray, Greeley, Hamilton and 12 more	2 hr
May 24, 2:42 PM MDT	Mesoscale Discussion	SPC	Gove, Logan, Rawlins, Sheridan, Thomas	63 min
May 24, 4:37 PM MDT	Mesoscale Discussion	SPC	Decatur, Finney, Gove, Grant, Hamilton, Kearny and 7 more	113 min
May 24, 5:39 PM MDT	Mesoscale Discussion	SPC	Decatur, Norton	36 min
May 23, 7:22 PM MDT	Mesoscale Discussion	SPC	Campbell, Corson, Dewey, Potter, Stanley, Sully and 1 more	53 min

Nearby

Mesoscale Discussions in Nebraska, 2021 Mesoscale Discussions in Colorado, 2021 Mesoscale Discussions in Kansas, 2021 Every mesoscale discussion in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.